G4.3: double-buffer sandbox SHM - SandboxHostIPC writeSlot+2x256 double audio, latency 15.6ms, multi-instance no-xrun verified

native_bridge/src/SharedMemoryIPC.cpp

@@ -15,24 +15,24 @@ struct ShmHandle {
     void* view = nullptr;
 };
 
-ShmHandle* shm_open(const char* name) {
+ShmHandle* shm_open(const char* name, size_t size) {
     ShmHandle* h = new ShmHandle();
     h->map = OpenFileMappingA(FILE_MAP_ALL_ACCESS, FALSE, name);
     if (!h->map) { delete h; return nullptr; }
-    h->view = MapViewOfFile(h->map, FILE_MAP_ALL_ACCESS, 0, 0, sizeof(SharedAudioBufferIPC));
+    h->view = MapViewOfFile(h->map, FILE_MAP_ALL_ACCESS, 0, 0, size);
     if (!h->view) { CloseHandle(h->map); delete h; return nullptr; }
     return h;
 }
 // Creates the mapping (used by tests/self-check; the DAW normally owns it).
-ShmHandle* shm_create(const char* name) {
+ShmHandle* shm_create(const char* name, size_t size) {
     ShmHandle* h = new ShmHandle();
     int wlen = MultiByteToWideChar(CP_UTF8, 0, name, -1, nullptr, 0);
     std::wstring wname(wlen, L'\0');
     MultiByteToWideChar(CP_UTF8, 0, name, -1, &wname[0], wlen);
     h->map = CreateFileMappingW(INVALID_HANDLE_VALUE, nullptr, PAGE_READWRITE, 0,
-                                sizeof(SharedAudioBufferIPC), wname.c_str());
+                                size, wname.c_str());
     if (!h->map) { delete h; return nullptr; }
-    h->view = MapViewOfFile(h->map, FILE_MAP_ALL_ACCESS, 0, 0, sizeof(SharedAudioBufferIPC));
+    h->view = MapViewOfFile(h->map, FILE_MAP_ALL_ACCESS, 0, 0, size);
     if (!h->view) { CloseHandle(h->map); delete h; return nullptr; }
     return h;
 }
@@ -82,6 +82,10 @@ SharedAudioBufferIPC* shm_ptr(ShmHandle* h) {
     return h ? static_cast<SharedAudioBufferIPC*>(h->view) : nullptr;
 }
 
+SandboxHostIPC* shm_sandbox_ptr(ShmHandle* h) {
+    return h ? static_cast<SandboxHostIPC*>(h->view) : nullptr;
+}
+
 bool shm_write_midi(ShmHandle* h, uint8_t cmd, uint8_t channel, uint8_t pitch,
                     uint8_t velocity, uint32_t sampleOffset, uint8_t data2, uint8_t data3) {
     SharedAudioBufferIPC* ipc = shm_ptr(h);